Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-30
2003-03-04
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06527372
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for controlling a driving input signal to efficiently utilize an ink jet head using shape memory alloy, and more particularly, the present invention relates to a method for optimizing a driving input signal in an ink jet head using shape memory alloy, which optimizes a waveform of a driving voltage applied to heat the ink jet head, without a structural alteration of the ink jet head driven by being heated and without a change in manufacturing processes for the ink jet head, thereby improving an ink firing characteristic and preventing the ink jet head from being overheated.
2. Description of the Related Art
Generally, printers are divided into a line printing type printer and a page printing type printer depending upon a printing scheme which they adopt. A so-called laser printer is representative of a page printing type printer, and a so-called dot printer or an ink jet printer is representative of a line printing type printer.
Drop-on-demand (DOD) type printer heads which fire liquid ink only under necessity are most widely used for ink jet printers. Use of such DOD type printer heads has gradually increased in that they require no electric charge or deflection of ink droplets and in that since high pressure is not needed, an easy printing is achieved by immediately firing ink droplets under atmospheric pressure.
Typical firing principles of such DOD type printer heads include a heating type firing method using a resistor, a vibration type firing method using a piezoelectric element, and a firing method using shape memory alloy, etc.
A printer head which adopts a heating type firing method generally includes a nozzle plate having a plurality of nozzles, a fluid passage plate coupled onto the nozzle plate and defining an ink storing chamber into which ink is stored, a substrate coupled onto the fluid passage plate and covering the ink storing chamber, and a heating resistor embedded into the substrate.
In an ink firing device of a printer head which adopts a heating type firing method, as shown in
FIG. 1
, ink is fired as described below.
First, if a predetermined voltage is applied to a heating resistor
14
, heat is generated. By the heat generated in the heating resistor
14
, air contained in ink adjacent the heating resistor
14
is expanded to create air bubbles. By these air bubbles, ink
16
inside an ink storing chamber
10
is forced out through a nozzle
12
to be fired toward a recording medium.
Accordingly, in the printer head which adopts the heating type firing method, bubbles such as lathers are generated when heat is applied to ink which is filled in the printer head, and the generated bubbles are fired through the nozzle to define a character on a printing sheet. Therefore, in the sense that the printer head uses air bubbles, the printer head is called an ink bubble jet type printer head.
However, the heating type firing method suffers from defects in that since ink is heated by heat generated in the heating resistor
14
, the ink is likely to be chemically degraded, and this degraded ink may be deposited onto an inner surface of the nozzle
12
clogging the nozzle
12
.
Also, since the heating resistor
14
repeatedly generates heat upon application of a voltage, a lifetime of the heating resistor
14
is shortened, and since only water soluble ink should be used, preserving property for a printed document is deteriorated.
A printer head which adopts a vibration type firing method, is generally similar in its structure to the printer head which adopts the heating type firing method, except that a piezoelectric element is disposed at a position where the heating resistor
14
is disposed in the printer head which adopts the heating type firing method (see FIG.
1
).
In an ink firing device of a printer head which adopts a vibration type firing method, as shown in
FIG. 2
, ink is fired as described below. If predetermined electric power is supplied to a piezoelectric element
24
, the piezoelectric element
24
vibrates. By the vibration of the piezoelectric element
24
, a volume of an ink storing chamber
20
is momentarily changed, and by this, ink
26
inside the ink storing chamber
20
is forced out through a nozzle
22
to be fired toward a recording medium.
The vibration type firing method using the vibration of the piezoelectric element
24
provides an advantage in that since heat is not used, it is possible to use an ink other than water soluble ink and thereby a greater variety of choices are offered for ink. However, the vibration type firing method is encountered with problems in that since workability for the piezoelectric element
24
is impaired and especially, it is difficult to form the piezoelectric element
24
, productivity is reduced.
FIG. 3
is a cross-sectional view schematically illustrating an ink firing device of a printer head which uses shape memory alloy. A shape memory alloy
32
which is in a flexurally deformed state is disposed above an ink storing chamber
30
. If the shape memory alloy
32
which is in the flexurally deformed state is heated, the shape memory alloy
32
is returned to its original flattened state after a flexurally deformed portion is smoothed out.
As the shape memory alloy
32
is returned to its original flattened state, a volume of the ink storing chamber
30
is decreased, and according to this, ink supplied through an ink supplying path
38
and stored in the ink storing chamber
30
is fired through a nozzle
36
to a recording device (not shown).
A printer head using shape memory alloy is classified into a first type wherein several shape memory alloy layers having different phase transformation temperatures and different thicknesses are coupled one with another to be flexurally deformed and a second type wherein a shape limiting body
33
and the shape memory alloy
32
are coupled with each other to be flexurally deformed. At this time, a member comprising the shape limiting body
33
and the shape memory alloy
32
which are coupled with each other is called a vibrating plate.
Because printer heads of these types employ shape memory alloy of a plate-shaped configuration which has a thickness of 50-1,000 &mgr;m and an area of 0.1-10 mm
2
, power consumption is increased upon heating, heating and cooling times are lengthened to decrease operation frequency, and printing speed is lowered thereby deteriorating practicality of the entire printer head.
Moreover, since the shape memory alloy layer is thick and wide, it cannot be instantaneously heated, and displacement is slowly generated over a relatively long period of time. Accordingly, due to the fact that a generated pressure is reduced, ink may not be fired or may not be properly fired. Also, even in the case that ink is fired, because firing speed of droplets is decreased, wetting may be caused and thereby it is difficult to achieve stable firing of the ink due to variations in velocity and size of ink droplets.
In addition, due to the fact that the shape memory alloy layer has a configuration of a plate which is large and thick and therefore, the entire structure thereof cannot but be enlarged, it is difficult to miniaturize the size of the printer head, integration density of nozzles is diminished and printing resolution is deteriorated.
In other words, in the case that the shape memory alloy is used as taught in the conventional art, a pressure chamber of the printer head must be enlarged such that it has a length of 100-10,000 &mgr;m and a width of 50-500 &mgr;m. Accordingly, if a pressure chamber of this size is used, the entire structure of the printer head cannot but also be enlarged.
Besides, since the printer head is constructed in that several shape memory alloy layers which are bonded one with another and bent, or a thin plate-shaped shape memory alloy layer and a shape limiting body which are bonded with each other and bent, are attached by bonding to a main body in which an ink storing chamber is defined, it is difficult to manufacture
Choi Hae Yong
Jung Myung-Song
Darby & Darby
Gordon Raquel Yvette
Samsung Electro-Mechanics Co. Ltd.
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